Nori's structural-rank conjecture for closures of algebraic-group subgroups

Let A\mathcal{A} be a commutative algebraic group over Q\mathbb{Q} that is either a torus or an abelian variety, with Lie algebra a\mathfrak{a} over Q\mathbb{Q} and exponential map

exp⁡:a⊗R⟶A(R).\operatorname{exp}:\mathfrak{a}\otimes\mathbb{R}\longrightarrow\mathcal{A}(\mathbb{R}).

Let L⊂A(Q)\mathcal{L}\subset\mathcal{A}(\mathbb{Q}) be finitely generated, torsion free, and of rank mm. For each finite prime pp for which its closure L‾p\overline{\mathcal{L}}_p in A(Qp)\mathcal{A}(\mathbb{Q}_p) is compact and contains Zpd(p)\mathbb{Z}_p^{d(p)} as a finite-index subgroup, define d(p)d(p) accordingly. Nori's structural-rank conjecture. The integers d(p)d(p) are independent of pp and equal the structural rank of the linear map Zm→a⊗R\mathbb{Z}^m\to\mathfrak{a}\otimes\mathbb{R} induced by log⁡L\log\mathcal{L}. This is proposed as a common-value refinement of Nori's question, with no resolution evidence supplied.

References

Primary source

Dipendra Prasad, “Some questions in Diophantine approximation: real and p-adics”, arXiv:2505.15744 (2025).

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